Retinal pigment epithelial (RPE) cells form part of the blood-retina barrier and have recently been shown to produce various chemokines in response to proinflammatory cytokines. RT-PCR analysis indicated that the predominant receptor expressed on RPE cells was CXCR4. The level of CXCR4 mRNA expression, but not cell surface expression, increased on stimulation with IL-1β or TNF-α. CXCR4 protein could be detected on the surface of 16% of the RPE cells using flow cytometry. (The Journal of Immunology, 2000, 165: 4372-4378.)